If a hand has to be amputated or has been irreversibly severed from an arm by an accident, the appearance and some of the function of the hand can be replaced by a hand prosthesis. For this purpose, the hand prosthesis must be capable of displacing gripping devices, which may be formed as replicas of fingers, in relation to one another, in order to allow gripping of an object.
Apart from a two-finger gripper, as is known from US 2003/00195638 A1, conventional hand prostheses have a drive that is rigidly connected to a hand chassis by means of a bevel gear mechanism. Depending on the direction of rotation of the drive, the finger prostheses are thereby moved toward or away from one another. This drive may be activated by means of myoelectrical signals. Such a hand prosthesis is described in US 2005/0021154 A1. The appearance of such a hand prosthesis looks less natural.